This large multicenter cohort study found that of the variables studied, increased immobilization time was the only independent predictor of residual elbow stiffness following medial epicondyle fractures in children, independent of treatment strategy and receiving PT/OT. With surgical treatment often warranting shorter post-treatment immobilization times, surgery may provide an avenue for consistently regaining full ROM when treating these fractures, especially in the setting of concomitant dislocation.